I've been playing around with customizing the e-mail templates in the WHMCS admin section. It would be tremendously useful to have a "Preview" button, with either the output of the template with demo user information, or a generated .pdf opening in a new window. I know I can perform an action, such as generating a new invoice or what not, but then I have to go through the motions of doing that. And some of the functions are just a pain in the arse to have to emulate.
So there you go, my first desired request. Please help WHMCS dev team!